These are ".wav" sound files (between 120kB and 700 kB) and should be recognised by most computer systems.
Sound1.wav : the first million years of sound (1 second = 100,000 years), held at constant volume, and shifted up approximately 50 octaves. Notice the three stages; descending scream, building roar, growing hiss.
Sound2.wav : similar to sound1.wav except the sound has been "doctored" to include only the central frequencies of the first eight harmonics. Otherwise the full pitch evolution is included.
Sound3.wav : similar to sound2.wav except the pitch is held fixed by anchoring the fundamental (first harmonic) to A220 Hz. All tones have been forced to the nearest note in a modern musical scale (which results in occasional steps as the tones slowly evolve).
Sound4.wav : raw sound constructed directly from the CMB sound spectrum, with harmonic frequency L replaced by acoustic frequency in Hz (hence the famous "first peak" at L = 220 contributes a fundamental at A220 Hz).
Sound5.wav : the raw CMB sounds from three different kinds of Universe; the first has low density and open geometry, the second has critical density and flat geometry, the third has high density and closed geometry.
Sound6.wav : this sound alternates between the raw CMB sound (sound4.wav) and the true sound present in the cosmic gas; ie with various distortions which affect the appearance of the CMB removed. Cosmologists refer to these two forms as C(L) and P(k) (L is an angular frequency projected on the sky, while k is a 3-D spatial frequency).
Sound7.wav : similar to sound1.wav, but for the first 100 million years with exponential time -- 2 seconds for each factor of 10 in time (100 -- 1000 years; 1000 -- 10,000 years; etc). This helps to hear the early times more clearly. Note that the volume has been held constant to allow the whole duration to be heard.
Sound8.wav : the pure sound emerging from inflation, prior to any modification by gravity or any other process. This has been generated using the "Initial Sound Spectrum"; thought to be a simple proportionality between loudness and frequency. This sound includes both very deep and very high frequencies, but overall sounds like a high pitched hiss to our ears. One can think of it as the original driving sound which sets the Universe vibrating, while the evolving sounds that emerge embody the resonant response of the Universe.